1. Field of the Invention
The present invention relates to a magnetic recording medium, a method of manufacture therefor, and a magnetic read/write apparatus that uses the magnetic recording medium.
2. Description of the Related Art
A magnetic recording medium, that is now commercially available, is exclusively an in-plane magnetic recording medium wherein the axis of easy magnetization in a magnetic film is generally oriented parallel to the substrate.
In the in-plane magnetic recording medium, there is a possibility that the volume of bits becomes too small when the recording density is increased and magnetic read/write characteristics are deteriorated by the thermal stability effect. Also medium noise increases under the influence of diamagnetism in the boundary of recording bits when the recording density is increased.
In a so-called perpendicular magnetic recording medium of which the axis of easy magnetization in the magnetic film is generally oriented perpendicular to a substrate, in contrast, recording magnetic domains that have clear boundaries can be formed due to less influence of diamagnetism in the boundary of recording bits even when the recording density is increased, and therefore noise can be reduced. Moreover, since the recording density can be increased even if the volume of bits is comparatively large, strong thermal stability effects are exerted, resulting in much attention to the perpendicular magnetic recording medium. Consequently, a structure of a medium suited for use in perpendicular magnetic recording has been proposed.
Recently, there has been increasing demand for high-density recording in the magnetic recording medium. For this reason, such a magnetic recording medium has been proposed as a layer made of a soft magnetic material, called a soft back layer, is provided between a perpendicular magnetic film that serves as a recording layer and a substrate so as to improve the efficiency of the flow or the magnetic flux between a single pole type head and the magnetic recording medium, in order to use the single pole type head that has high capability of writing in the perpendicular magnetic film.
However, even when the soft back layer is provided, the magnetic recording medium does not have satisfactory performance in the read/write characteristics, thermal stability and the resolution of recording, and therefore a magnetic recording medium that is better in these characteristics has been required.
Japanese Patent No. 2669529 proposes to enhance lattice matching properties between a Ti undercoat film and a Co alloy magnetic film and to improve the orientation of the c axis of the Co alloy magnetic film by introducing the other element into the Ti undercoat film.
However, when using a Ti alloy undercoat film, the magnetic cluster size in the Co alloy magnetic film increases and the medium noise increases, thereby making it difficult to further increase the recording density.
Japanese Patent Application, First Publication No. Hei 8-180360 proposes to improve the orientation of the c axis of the Co alloy magnetic film by using an undercoat film comprising Co and Ru.
However, the mean crystal grain diameter of the undercoat film comprising Co and Ru increases. As a result, the magnetic grain diameter in the Co alloy magnetic film increases and the medium noise increases, thereby making it difficult to further increase the recording density.
Japanese Patent Application, First Publication No. Sho 63-211117 proposes to use a carbon-containing undercoat film.
However, when using the carbon-containing undercoat film, since this film has an amorphous structure, the orientation of the c axis of the perpendicular magnetic film deteriorates and the thermal stability deteriorates, thereby making it difficult to further increase the recording density.
Under the above-described circumstances, the present invention has been made, and an object thereof is to provide a magnetic recording medium that is capable of recording and read backing information at a higher density by improving the read/write characteristics and thermal stability, a method of manufacture therefor, and a magnetic read/write apparatus.